Large-scale spatiotemporal variations, sources, and risk assessment of banned OCPs and PAHs in suspended particulate matter from the Negro river, Argentina

Organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) threaten the environment due to their wide environmental resistance. Environmental paradigms coexist along the Negro River (NR) in Argentina, South America, which flows to the sea below the latitude of 40o S; however, this is the first environmental assessment of OCPs and PAHs in water of the NR for more than 15 years. With 21 sampling sites covering a range of 600 km of river extension, we assessed 16 OCPs and 16 PAHs in suspended particulate material (SPM) with regard to their levels, seasonality, sources, and potential biological risk assessment. Using gas chromatography-mass spectrometry and gas chromatography coupled with electron capture detection, we found an overall mean value for sigma 16 OCPs of 648.56 ng. g-1, d.w. Despite a ban spanning 25 years, an increasing trend of accumulation of hexachlorocyclohexanes (HCHs) and endosulfan was shown in the lower valley. The alpha-HCH/?HCH and beta-HCH/(alpha + ?)-HCH ratios indicated a prevalent usage of technical HCH over lindane and recent HCH inputs. The most abundant compound, alpha-endosulfan, averaged 141.64 ng. g-1, d.w. and DDX (sigma 4,4 & PRIME;-DDE, 4,4 & PRIME;DDD, and 4,4 & PRIME;-DDT) averaged 99.98 ng. g-1, d.w. Winter OCP loads in the NR reflected the runoff of the heaviest pesticide application period. We estimated the total discharge of DDT into the Atlantic ocean was 96 g.day- 1, added to 458 g of HCHs and 257 g of endosulfans (alpha + beta + epoxide) adsorbed by the SPM. PAHs occurred widely along the river (38.83 & PLUSMN; 43.52 mu g. g-1) and the highest levels coincided with locations with marked anthropogenic-related activity, such as petroleum/gas exploitation facilities. Risk quotient analysis showed a low risk posed by OCPs, but a high risk of potential effects on biota posed by the PAHs, highlighting the need for mitigation measures.

Automated summary

This study assessed the levels, sources, and potential biological risks of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in the water of the Negro River in Argentina. It found an increasing trend of OCP accumulation in the lower valley and widespread presence of PAHs along the river, particularly in areas with anthropogenic activity. PAHs posed a high risk to biota, highlighting the need for mitigation measures.